Windshield wiper mechanism



April 3 1951 c. R. SACCHINI 2,547,175

WINDSHIELD WIPER MECHANISM Filed Dec. 30, 1947 v s Sheets-Sheet 1 :jimllmmm INVENTOR. COL 101503 F. Sna /1w Q Afr Tami/EV April 3, 1951 c. R. SACCHINI 2,547,175

WINDSHIELD WIPER MECHANISM Filed Dec. 30, 1947 e Sheets-Sheet 2 A TTU/FA/E Y April 3,- 1951 c. R. SACCHINI 2,547,175

WINDSHIELD WIPER MECHANISM Filed Dec. 30, 1947 6 Sheets-Sheet 3 IN V EN TOR.

('04 u/va (/5 fPS/ICCH/IV/ BY 14 g ATTORNEY April 1951 c. R. SACCHINI 2,547,175

WINDSHIELD WIPER MECHANISM Filed Dec. 50, 1947 6 Sheets-Sheet 4 79 4 INVENTOR.

COLUMBt/J P. SAccHM/I A TTOEA/E r April 3, 1951 v c. .R. SACCHINI 2,547,175

WINDSHIELD WIPER MECHANISM Filed Dec. 30, 1947 6 Sheets-Sheet 5 v 7/ GM A l III II INVENTOR- (bu/rmz/s f? SAC'C'H/N/ Ap 1953 c. R. SACCHINI WINDSHIELD WIPER MECHANISM 6 Sheets-Sheet 5 Filed Dec. 30, 1947 mi Q, L

I II INVENTOR ('01. unfit/J Sara/(NI ATTORNEY Patented Apr. 3, 1951 WINDSHIELD WIPER MECHANISM Columbus it. Sacchini, Willoughby, Ohio, assignor to The Marquette Metal Products Company, Cleveland, Ohio, a corporation of Ohio Application December 30, 1947, Serial No. 794,551

(Ci. (ac-9'2) 9 Claims.

This invention relates primarily to a fluidoperated mechanism adapted for oscillating or reciprocating one or more windshield wiper blades over a surface or surfaces to be cleared. The

V principal novelty, indicating one object, resides in the provision of an improved automatically acting fluid motor actuator unit supplied with pressure fluid from any suitable source and arranged to divert pressure fluid alternately to opposite ends of a closed loop reciprocating servomotor mechanism and to eXhaust spent fluid alternately from said ends. The servomotor mechanism as shown hereby comprises a plurality of cylinder and piston units connected for example in series, spaced any desired distance apart and arranged to operate windshield wiper drive arms in synchronism; a further object being indicated by the fact that, regardless of the number and spacing of piston and cylinder employed in the system, the quantity of fluid consumed at a given speed in a given period of time p is the same.

A further object is to provide a relatively simple and accurately operatin fluid-reversing valve mechanism for supplying operating fluid to a plurality of reciprocating servomotors adapted to operate in a closed loop circuit and wherein blocking of the normal operation of one only of the servomotors s rior to reaching the end of its normal stroke will cause the mechanism to continue in operation at full strength for eiiecting shorter than normal strokes until the cause of such blocking is removed.

Another object is to provide an improved and simplified fluid-operated reciprocating window wiping servomotor unit capable of being used singly or in pairs or groups connected in series with each other and, in event of such series 'connected arrangement, maintainable normall and automatically in synchronism.

Further objects include provision of a window unit piston and cylinder mechanism which when used in pairs or any plurality connected with an automatic actuator or reversing valve unit rendered operative to efiect reversal of fluid flow motor actuator unit for reversibly supplying and exhausting operating fluid in respect to one or more reciprocating servomotors wherein the reversing operation is accomplished by the use of two spring biased pressure operated valving 'plungers or plunger assemblies so arranged that pressure build-up in the system to a predeterminable point causes the reversing operation to take place irrespective of length of stroke on part of the. servomotor or motors.

Another object is to provide an improved window or windshield wiping system operable by fluid pressure under the control of a master actuator unit and wherein parking of the wiping element or elements in a particular position or positions results merely from gradually restricting and then closing a fluid supply valve leading to the actuator unit, which supply valve is also operable to adjust the speed of operation of the wiping mechanism.

A specific object is to provide a reversing valvemechanism such as outlined above wherein the moving parts are few in number, simple in construction and capable of being easily assembled in properly working relationship.

Other objects and features of the invention will become apparent from the following description of preferred embodiments. I

In the drawings, Fig. 1 is a diagrammatic assembly view showing the present invention arranged for controlling two'wiper-blade-reciproeating window units connected in series with each other; Fig. la is a relatively enlarged sectional View of a speed control and fluid shut-oiT valve.

Figs. 2, 3 and 4 are enlarged sectional assembly views respectively showing the parts of the reversing mechanism and window units in different operating positions. Fig. 5 is a view corresponding to the lower part of Fig. 2 showing a modified fluid-reversing mechanism; Fig. 6 is a longitudinal central sectional View of a window unit plunger and cylinder assembly, and Fig. 7 is a cross sectional view taken as indicated on line 'El' of 6. Fig. 8 is a view corresponding to Fig. 6 showing a modified form of window unit piston and cylinder assembly.

Master actuator unit (construction) Referring to .Fig. l, a master actuator unit i supplies the window unit assembly 2 comprising, in the illustrated arrangement, two identical servomotor or window wiping units A and B (3 shown in reduced scale) having their inboard ends connected together by suitable fluid transmission conduit means such as a tube C. The

outboard end of unit A is connected as by the tube D to a service port A of the actuator unit I. The outboard end of the unit B is connected by a similar tube E to a service port B of the actuator unit.

The actuator unit 1 is supplied through a main speed control and shut-oil valve 3 (Figs. 1 and 1a) controllable as by a handle said valve being connected as by a tube F to a pressure inlet port G of the actuator unit. An exhaust fluid outlet port H of the actuator unit i is connected as by a tube J to a reservoir portion of the pressure supply system (c. g. pump, accumulator, etc., not shown).

As indicated by the arrow on tube F, pressure fluid always moves from the control valve toward the pressure inlet G of the unit 2 but the fluid as indicated by the arrows on tubes D and E 7 moves in either of two directions in each of those tubes depending upon the instantaneous direction of motion on part of the window units A and B. Each of said window units A and B shown in Figs. 3 to l (B shown in section in Fig. 6) has a power piston in a cylinder 5! and power takeoff means such as a toothed pinion or sector 7 (cf. Fig. 7) in mesh with corresponding teeth of the piston; and the pinions or sectors 2 are drivingly rigid with shafts lot for supporting respective oscillatable wiper drive arms 8. The window units A and B are exactly alike, wher fore only one will be described in detail, the corresponding parts of both units being given the same identifying characters.

Referring to the actuator unit this comprises a suitable generally rectangular metal body iii having main parallel bores H and i2 there-- through in whi h are p ably located and fixedly secured laterally ported valve sleeves l5 and i5 respectively. The ends of the bores ii and I2 are closed by suitable sealing'plugs indicated H, i 8, l9 and 2B, the plug 26 being or" special form in that it constitutes a housing for a valve return spring later described. The main bores ii and i2 are intersected by various cross passages, the

positions and different portions or which will he referred to as upper, lower, right, left, etc. for reference purposes only. The unit I an i the window units will, of course, operate in any conceivable position.

The pressure fluid inlet port G, Fig. 1, communicates with the body It! at a short main cross inlet passage 2!, igs. 2-4, located between the bores H and i2. The outlet port H, Fig. 1, constantly communicates with a cross passage 22, Figs. 2-4, in the body.

The fixed valve sleeve l5 slidabl contains a main or master fluid directing valve plunger which for simplicity will usually be referred to as the directional valve. The fixed valve sleeve l6 similarly contains a cooperating fluid directing valve plunger or slave valve 26. Cross ports in the sleeves and body connect the cooperating valve bores 25' and 28 in the sleeves. Before admission of minimum operating pressure to the unit (e. g. 1100 p. s. i.) the directional valve 25 occupies the normal or inactive position shown in Fig. 2, said valve being spring biased into that position as by a coil spring 2'? located in the right hand portion of the bore H unoccupied by the valve sleeve E5. The corresponding normal or inactive position of the slave valve 26 is as shown in Fig. 2, said valve being spring biased into that position by a coil spring 28 contained within the hollow plug 22. The springs act inwardly opposite directions against respective shoulders and 28' of the valve plungers, which shoulders abut associated ends of the fixed valve sleeves l5 and 85 as stops.

In order to move the slave valve out of its normal position, the end thereof opposite the return sping 28 is abutted by a stem portion 3c of a positioning servomotor plunger or piston 3| con tained in a fixed sleeve or working cylinder 32 peripherally sealed in a countercore portion of the bore l2. Full diameter land portions 35, and 35 of the servo cylinder 32 are in sealed relation to the counterbore and the plug it holds the cylinder against the bottom of the counterbore. The servcmotor piston 3! is shown in its normally occupied position in Fig. 2 being intermediate the effective ends of the cylinder pressure chamber by virtue of the spring 28 acting on the slave valve 26 and therethrough on the stem .33 of the positioning servomotor plunger.

The cross passages necessary to communicate the supply and exhaust passages 2i 22 with the directional valve and slave valve and with the service ports A and B may comprise vertical cross drillings as at 52, it, 12, and (left to right) which intersect the main body bores H and i2 and extend upwardly therebeyond for communication with one or the other of the service ports A and B. The upward extensions of the passages it ll and 2 communicate with service port A, leading to the outboard end of the window unit A, partly by intersecting a longitudinal drilled passage 4% in the left end of the body it: passing through the service port A. The vertical passage 13 terminates upwardly at the service port B to which a longitudinal drills passage :5 similar to the passage A l extends the right end of the body. The relatively outer ends of all the passages from as to 65 mi. suitably plugged as indicated. Portions 6, 6, etc. of the vertical passages 4%, ii and G2 align and communicate with associated radial valveport-forming holes in one or both of the valve sleeves l5 and is. The portion :23 of the passage 33 connects at the upper end with full diameter pressure chamber portion oi bore !2 Which receives the slave valve sleeve. The lower end of the portion 53 connects with a longitudinal slot 6% in the upper wall of the directional valve sleeve E5. The left end of the slot connects with a short radial passage d! leading into the directional valve sleeve bore 25 so "hat the vertical cross passage '53 has two axially spaced port openings through said sleeve. The longitudinal passage at the upper right portion of valve body ill, intersects an oblique passage 48 which in association with suitable circa... ferentially spaced ports in the servcrnotor cylinder sleeve 34' is constantly open into the servomotor cylinder pressure chamber 32'.

The main exhaust port 212 of the body I23, in addition to intersecting the cross passage portion 4!, is intersected by a longitudinal passag 50 formed in the body beyond the inner end of the pressure inlet port 2! and extending to the right of the exhaust port. lhe passage intersects a cross passage 5! between the main valve bores, which cross passage intersects an ohli ue passage 52, one end of which extends to the chamber 53 containing the directional valve return spring 21. Said chamber 53 is always in open communication with the lower end of the vertical passage 53 through a short oblique bore 5% in the body so as to connect the service port B with the exhaust port 22 in the normal position of the directional valve. The upper end of the oblique passage 52 exhaust port 22 through the longitudinal bore 59.

Thus the servomotor piston 3| is free to move to the right under the influence of the slave valve spring 28 when the directional valve is in its normal or initial position.

The various port closing lands of the directional valve plunger 25 are numbered 30 to 93 from left to right. The valving lands of the slave valve plunger are similarly numbered 95 to 99.

To provide for fluid actuation of the directional valve or plunger 25 into its circuit-reversing position and retaining of said valve in that position during the necessary part of the complete cycle of operation, a pressure chamber Hill is formed at the left end face 90 of the directional valve plunger. The chamber is defined by the plug 81, bore H, valve sleeve I5 and the face 93 of the valve plunger; and an oblique passage ml, and portion 49' of vertical passage is communicate the pressure chamber N30 with the interior of the slave valve sleeve I6 through a cooperating portion, said valve sleeve registering with passage portion M. Additionally said cooperating port in the slave valve sleeve is intersected by a longi- Window units (construction and operation) The window units A and B, as illustrated, are operatively identical at opposite ends, hencereversible end-for-end in the system. Referring'to the window unit A (Fig. 2, for example) the service tube D communicates'with the outboard end of the cylinder 9 through a suitable fitting 50 threaded and sealed to the cylinder. The opposite end of the cylinder 9 has an identical fitting 6B for connection with the tube 0. Each end of each cylinder 9 contains a dashpot mechanism or unit 62. Those are of identical construction to be described presently.

Assuming operation of the system has caused the piston 6 of window unit A to be brought to the position thereof shown by Fig. 3 and that operating pressure is established in the service tube D, operating pressure is built up in a chamber 63 defined in part by the adjacent end of the piston 9, in part by the fitting 60 and in part by the central bore of an annular dashpot cylinder member 65 clamped between'the window unit cylinder 9 and thefitting 6!! at a'flange portion 61 of cylinder 65. The d'ashpot and check valve cylinder members 55 and their associated check valve plugs (to be described) are oppositely positioned at opposite ends of each window unit cylinder 9. An inner sleeve portion se of each dashpot cylinder 65 slidably receives, with a few thouisandths of an inch total clearance, a cylindrical extension I2 of the piston 6 at the end of respective -strokes of said piston.

Each dashpot unit 62 is constituted by one of the piston extensions l2, an associated sealing cup or ring 15 on the piston, sealingly fitting the bore of cylinder 9, the adjacent portion of the main cylinder wall and the flange 51, which latter during dashpot action is closed against outward passage of fluid therethrough by check valves 68, 10 in the flange.

The illustrated check'valve arrangement comprises small check valve port openings 68 through each flange 61, the inner ends of which openings intersect suitable valve seats formed by counterbores in said flange. The counterbores form valve chambers for the plug elements it, shown as spherical, which plug elements are held against falling out of their chambers by a common snap ring ll embracing the sleeve portion 66 of the dashpot cylinder member.

At the beginning of each stroke of each piston 6, assuming continuing operation, the sleeve portion of the dashpot cylinder (left of window unit A, Fig. 3 for example), is momentarily occupied by the reduced diameter cylindrical portion or extension 12 of the piston. Since the check valves, just describedfopen toward the piston, pressure fluid entering the chember E53 opens the check valves and exerts pressure on the full diameter end area of the piston before the extension 12 is withdrawn from the dashpot.

The pistons ii are axially chambered at for nearly their entire length, being bored nearly therethrough from one end and the open ends of the bores then suitably plugged as illustrated. Very small radial priming passages 82 (e. g. diameter) at opposite ends'of each piston communicate with the chambers 8d. The radially outward ends of the priming passages K22 intersect the peripheries of the piston extensions 62 so that the passages are open during the principal parts of the piston strokes out substantially closed by respective dashpot sleeves 65 near the ends of the piston strokes.

"When the piston extensions 72 enter the sleeve portions 66 and close the priming passages 82, the

check valves seat and establish generally closed annular fluid spaces 69 (left, Fig. 3), the only in stantaneous outlet of which is along the extension F2 and the bore of the sleeve portion entered by the extension. Thus the cushioning action of the dashpot units at the end of each stroke of each piston in either direction is one of forcing operating fluid through the associated clearance space around a piston extension 72.

Assuming the entire system has been charged with operatingfluid and that the pistons 5 are similarly in parked positions in their cylinders 9, it will be apparent that fluid alternately admitted to 1 and simultaneously exhausted from units A and B will cause synchronous operation of the drive arms 8. That operation will continue'so long as the units A and B are nearly equally loaded, notwithstanding the fact that during'the larger part of each stroke of each piston a throttled orrestricted by-pass fluid circuit is established from tube D to tube E through the priming passages 82 and piston cavities 89. Now assuming that (as by local accumulation of ice on the windshield) an excessive load is imposed on the piston 6 of unit A, while it is travelling to the left, preventing the piston from performing a full stroke into the position illustrated in Fig. 3. Such overloading of unit A piston, if of suflicient magnitude to stop that piston in some mid-stroke position, will ordinarily cause a re-cycling of the actuator unit -i before either piston has com- 7 pleted its stroke. Now because both pistons have the same open throttled communication through the priming passages 82 and piston cavities 8!], more r'iuid will travel through the throttled passages of unit A piston than through those of unit 3 and the drive arm or unit B will begin to overtake the drive arm of unit A thus getting out of synchronisrn therewith. If the excessive loading is not removed the two window units will continue to perform short strokes with concomitant overtaking incre nents occurring on each cycle until the overloading is removed or operation is discontinued. After removal of the overload the piston of unit A will automatically attain its synchronized position in a short time as foll we: As surnin' piston E or" unit A is leading the piston of the companion unit B during travel of the two toward the left, the unit piston will first come to the end of its str he by closing its left hand primer passage 82 cause re-cycling of the actuator mechanism .i, since re-cycling as already indicated and more fully explained below is a function of rise in fluid pressure in either of the service tubes D or E. The unit 1-3 then exhausts through tube E and normal operating fluid pressure in tube 1) begins movement of both pistons E toward the right. Since the piston of unit A at the beginning of the rightward stroke is sealed at its left hand pr mer passage 82 the initial movement of the unit A piston will occur without any loss of fluid through its primer passages whereas the unit B piston will have such fluid loss and will not on that stroke be moved as far a the unit A piston will be moved. During succeeding strokes to the right the same phenomenon occurs until the two window units again -perate in synchronism.

The window unit system obviously operates in the same manner if the p'ston of unit B becomes blocked against full stroke movement. In order initiaily to charge the system with operating fluid it is only necessary to operate the mechanism until all pocketed air driven out of the exhaust line of the actuator unit. That ordinarily takes only a-few cycles of operation.

General operation Referring to Fig. which, stated above, shows the various parts i cluding the window unit servomotor pistons 52 normal or initial (parking) position, W1 be seen that the main inlet pressure port 2! of tne body communicates throu a the passage 2 with a Jacked portion of the slave valve plunger between lands 9% and thereof, thus, through the body passages 62" and i applying operating pressure to fluid in the tube 33 tending to move the piston of window unit A to the right. Any movement of said piston to the right also moves the piston or" window unit B to the right through the intermediary of the column of fluid in the tube C and associated connections. Admission of such pressure fluid is enabled by concurrent establishment of an exhaust circuit from the window unit 3 through the service port B, cross passage portion 43",, chair or it 'i constituted by the right end of slave valve bore i2, passage portion A. then aligned necked portion of the directional valve plunger between lands and 93 thereof, oblique passage 54. spring chamber 53, oblique passage 52, cross passages 55 and longitudinal passage 58 leading to the exhaust port 22.

Assuming the window unit pistons 6 are in some position other than their right hand or parking positions, they will, by establishment of.

the described fluid circuits, be driven to the right hand ends of their respective cylinders 'until the right hand dashpot piston portions i2 enter the corresponding dashpot sleeves 66. Thereupon motion of the pistons will be gradually arrested. The inboard check valves ii! of window unit A and the outboard check valves of window unit B close approximately when th projections '12 enter the dashpot sleeves. Arrest of piston movement in either direction usually occurs (at least at high operating speed) when the piston portions 22 have fully entered the dashpot sleeves to the positions shown, since some fluid can escape from the dashpots around the piston portions 52 and some through the check valve ports before the plugs is are fully seated.

As soon as either window unit piston is arrested as by the right-hand dashpots 82 or from any other cause, such as blocking of a wiper arm prior to full stroke thereof, pressure in the supply circuit leading to the service tube D immediately rises with the following results: Pressure fluid moves in the cross passage Ail and it as enabled by the position of slave valve lands 25 and SB shown on Fig. 2; and thereby, through th oblique passage raises the then existing pressure in the chamber Hi6 at the aft end of the directional valve plunger 25. The pressure rise in chain oer iflil causes movement of the directional valve plunger to the right until the port passage 4'! communicating with the longitudinal slot 45 of the directional valve sleeve i5 is at least slightly opened. Said ovenient oi"; the directional valve plunger causes its land $2 to cut oi the portion of the exhaust circuit for window unit B constituted by the lower end of the cross passage A3.

As the directional valve stroke just described is completed, pressure fluid is admit ed to the intermediate portion of the cross passage 43, thence to the chamber 565 between the slave positionin piston and cylinder assembly and the slave valve plunger and thence to the outboard end of the window unit B. Concurrently, operating fluid pressure from the service port B is established in the longitudinal bore '45 (upper right of body iii) oblique passage 48 etc. leading to the servomotor pressure chamber 32'. The pressure acts upon the servornotc-r piston 31 moving it to the left for its full possible stroke as evident from Fig. 3, moving the slave valve 28 to the position shown by Fig. 3. Said movement of the slave valve, as shown by'cornparison of Figs. 2 and 3, cuts oil the previous operating pressure supply to the tube D betw en lands 98 and 99 of the slave valve and opens cross passage portions 45 and ii to communication between the lands 9? and $3 or" the slave valve. Additionally the land E5 oi the slave valve now closes the cross passage portion 58' leading to the directional valve chamber i653 (lower left of body it!) thus hydraulically restraining the directional valve against return movement by its spring 2?. Opening of the cross passage portions ii and M establishes, through longitudinal passage port A and tube D, an exhaust circuit for the out.- board end of window unit servornotor A as will be evident from Fig. 3.

As the slave valve plunger 26 moves to the left beyond the position necessary to trap fluid in the chamber lot, as described, the portion of said plunger which projects into the. return spring housing 2!} forces fluid from said housing through the eccentricpassage H32, passage 35 and duct it! into the pressure chamber H3O adding to the fluid trapped. in said chamber and forcing the di- .unit pistons a restraint at port ll would have caused a loping movement of the wiper arms 5, i. e., faster in one direction than in the other.

fhe pressure and exhaust circuits established "as described above causes both pistons 6 to be driven to the left into the positions shown by Fig. 3 or some intermediate stopped position, assuming in the latter case that movement of one or the other of the wiper arms has been effectively blocked short of its full stroke. Pressure now rises in the pressure supply circuit leading to the window unit B, and since the slave valve positioning 'servomotor piston 3i cannot be moved any further to the left, the increased pressure acts on the right hand end piston face surface ilfi of the slave valve plunger. The slave valve plunger is thereby moved into the position thereof shown in Fig. 4 wherein the neck between the lands 96 and 9'! opens the cross passage lb allowing the theretofore trapped fluid in the pressure space 90 to return to sump pressure by way of exhaust through service port A, longitudinal passage t4 and cross passage ii. Said leftward final movement of the slave valve plunger simultaneously establishes (partly by the same port opening op- -rations) an exhaust circuit for the outboard end of the window unit cylinder A, the fluid path being A, 6 5, All, 6! to 22. The spring 2'? of the directional valve now returns the directional valve plunger to its initial position as shown on Fig. 2, opening the port 43 to vent the space Hit; and the slave valve spring 28 then returns the slave valve plunger and the slave valve positioning servo: motor. piston 31 both to their original positions. The exhaust circuit for window unit A, through tube D, is broken by the land 9'? of the slave valve (see Fig. 2) the neck between slave valve lands 98 and 9G reestablishes the pressure supply circuit to the outboard end of the window unit A, the returned directional valve plunger having completed reversal of the circuits as already described.

1 ill) While the system as shown in Fig. 1 and others operatesto move the window unit pistons simultaneously in the same direction, thereby swinging the blades simultaneously from left to right and from right to left, either of the window units A or B can be inverted (turned 189) without reconnecting the various tubes in order to make one drive arm 8 move to the right as the other drive arm moves to the left. In such case the drive arm of that unit is reconnected toits drive shaft in a 28 tend to re-position the directional valve and slave valve as shown in Fig. 2 irrespective of the positions of the valves at the time the supply of fluid is reduced below the minimum operating pressure.

Assume first, movement of the window unit pistons 6 to the right at the time the valve 3 operates to throttle the supply flow. During attempted recyling of the actuator unit after the pistons reach the Fig. 2 positions, leakage from the chamber I09, along the piston land to exhaust via the neck between lands 90 and 9 becomes at least as great as the input flow through the control valve 3, hence the pistons stay in the Fig. 2 positions.

If the fluid input is so reduced or throttled by the control valve 3 during movement of the window unit pistons to the left (actuator valve mechanism parts as in Fig. 3) suchleakage from chamber it!!! along the land of the directional valve, by enabling spring return of said valve until port G7 is out off, stops further movement of the window unit pistons to the left and then, by opening the valve ports of vertical passage 33, re-establishcs an exhaust circuit for the outboard end of Window unit B. Thereupon the spring 28 returns the slave valve to its Fig. 2 position completing the reversal of the supply circuit to the outboard end of window unit A. Meanwhile momentary continuance of fluid supply at low rate, during the remainder of the normal operation of shutting off of the control valve, causes return of the window unit pistons to their right hand positions. The low rate fiuidsupply, under the conditions men- .tioned, is insufficient to offset the leakage from chamber iflil and theactuator unit cannot recycle. 7

In order to cause the drive arms -8 to become parked at the right (pistons E to left) instead of in the illustrated parked position (Figs. 1 and 2) the service tube connections to the actuator unit l are reversed. The tube D is connected to service port B and tube E to service port A.

It will be evident that the strength of the directional valve spring 2? determines to torque output of the window unit mechanisms. In case of a relatively weak spring 27, the re -cycling of the actuator mechanism, final step of which is illustrated by Fig. 4, will occur with a less rise in pressure in the service system operating to force against the directional valve plunger face 9% than in the case of a strong spring El. The strength of the return spring 28 for the slave valve has only to be slightly more than sufficient to overcome friction of the valve plunger and sleeve surfaces.

Fig. 5. Constructio n The modification of actuator unit shown by Fig. 5 enables positive and accurately timed operation of the valves at reduced operating pressure as compared to the minimum pressurerequired for the previously described arrangement. All parts are formed the same as before except for the slave valve 260. and its sleeve Kid. The parts are in the relative (normal) position corresponding to Fig. 2. A U-shaped passage 262 in sleeve l6a replaces the passage I62 in the valve sleeve l6 and provides an additional port 2113 opening into the bore of the sleeve in spaced relation to the port formed by extension of the portion 40 of bore 48 through the wall of the slave valve sleeve. Additionally a relief bore 284 extends from the left end of the slave valve axially thereof and has a communicating lateral passage 205 open between lands 95 and 96 and an additional passage 206 open between lands 97 and 98.

Fig. '5.Operation When the slave valve is moved leftward to its first operating position (same as in Fig. 3) to trap operating pressure fluid in the chamber space we, thereby temporarily to retain the directional valve in its Fig. 3 position, from the pocket housing the slave valve spring 23 is first vented from the pocket by way of bore 2% and passage 2'55 and then by way or the passage 2532 to boost the reversing-valve-holding pressure in the chamber and assure full opening of the port i? in the reversing valve sleeve. As soon as the land as cuts on passage 233 the neck between lands 9? and 93 of the slave valve opens the axial bore 2% in said valve to exhaust pressure at ii thus allowing completion of the first movemen (of. 5) of ve valve. slave vc spring pocket during that movement is cut from communication with the chamber its when land 95 closes the port 253 in the slave valve sleeve.

Reference to Fig. 3 and associated description of operation shows that the slave valve 26 is moved to its Fig. 3 position by pressure in piston chamber space 32' which pressure causes leftward movement of the window unit pistons. Prior to commencement of movement of the pistons of window units A and B to the left, the pressure in service line hence chamber 32, is hi her than after the pistons start to move. The pressure drop consequent upon movement of the pistons is occasioned by the difierence between static and dynamic friction force. When the pressure drop occurs in chamber 32' there is a sligt movement of the slave valve 26 with its operating piston 35 to the right. That results in a momentary lowering of the pressure in chamber i248 and consequent sli ht movement of' the directional valve 25 to the left. It the operating pressure is very low the movement just de scribed is apt to cause the port ii to be throttled by the valve land 92, and thereby an instantaneous slowin down of the leftward movement of the window unit pistons. Pressure immediately raises again in the service line E causing repositioning of the slave valve and directional valve and the window unit pistons move further to the left. Therefore, if the operating pressure in the system happens to be low, the leftward movement of the window unit pistons is unstable and jerky. Since in the Fig. 5 construction the pressure chamber His is not in communication with the chamber space which houses the slave valve spring 23 it follows that during such leftward movement of the window unit pistons as described there is no Such unsteadiness of operation even at low fluid pressures.

M odified window units Referring to Fig. 8 the view shows a window unit construction Hi3 enabling more effective locking of the wiper or wipers in parked or stopped positions than enabled by the construction previously described and as shown for example in Fig. 2. The construction also enables movement of the piston of one of (e. g.) two serially connected similar window units to continue operation when the wiper arm of the cooperating unit ,ecomes stalled or blocked, regardless of the position of either piston in its cylinder when blocking occurs. Each window unit used in the system is identical with the one shown.

So far as the unit are of Fig. 8 has parts substantially identical with counterparts of unit A, Fig. 2, for er; .mple, those parts have the same identifying members as already given. The power piston H6 is shown in a position midway of the cylinder s so that the two reduced diameter extensions of the piston are disengaged from their cooperating dashpot sleeves i 18 which those extensions slidably enter aS the piston approaches 5 respective ends of its strokes. The priming passages 52 (see Fig. 2) and other parts are omitted from the piston in? and, instead, priming fluid can by-pass the piston through a double check valve system and cooperating vent passages arranged as follows:

Ehe piston has a central through bore I20 closed at its opposite ends by tubular check valve fittings iii sealed into the extensions ill and threaded to respective ends of the through bore. The fittings 525 have valve-seat-forming central bores or passages I22, open to their outer ends, and counterbor-es 223 in which spherical valve plugs (e. g. metal ball 12s and M5) have free sliding fit. Sleeve portions 528 of the fittings l2! are smaller than the bore 529 from the inner ends of the fittings to points beyond the valve seats, and restricted lateral passages 52! and Q28 lead from the valve chamber spaces around the spherical plugs into the spaces surrounding the fitting 1t: sleeve portions 525. Those spaces are in free communication with a cross bore 29 in the piston body lit leading to free spaces at each side of the piston as indicated at 29 on Fig. 7 showing the previously described form. Those free spaces 529' are in somewhat restricted one-way communication with the pressure space at each end or" the cylinder past respective seals 15 of the piston. Fluid, in other words, is permitted restricted flow from, for example, the left hand pressure chamber ass through the associated bore I22, past the check valve plug i2 -l through the vent I21 and finally into the pressure chamber i3! past the right hand piston seal '15. Restricted flow through the piston is likewise permitted in the opposite direction.

mainto the bores ich maintains are ct recycl- 't For to cause E32 would about 3-3.) p. s. i.

ihe cushioning dashpot action, when the extensions i il of the piston. enter respective sleeves IE3, is due to provision of res. .cted passages [3 and its in the dashpot sleeves which discharge fluid at a relatively slow rate from the sealed spaces around the piston extensions they enter the sleeves.

Assuming the illustrated window unit of Fig.

8 serving as ur A in Fig. 1, the left hand V is connected to the supply and exhaust line D the i Fig. l and the right hand fitting is cured to window unit conof unit 3. The operation (at cylinder fittin 53 e pipe in normally drives the e illustrated unit A to the right he connecting pipe C driving the unit B to the both to the g rcve .i or recyclve mechanism as already d rib-ed. If at compl tion of the strokes of he stons to the left the wiper of unit B becomes sailed in end stroke position its piston will not 13 move from the inboard position. Thereupon the inboard (left hand) ball valve wt of unit B is forced on its seat, the check valve spring .l32 havinginsuflicient force to effect recycling of the actuator i. The resuling restricted flow through vent I21 past the unit B piston enables iull stroke operation of the unit A piston to the ri ht until the inboard end or that piston enters its'dashpot and completes the rightward stroke, thereby causing recycling of the actuator unit 6. Then, if the piston of unit B remains stalled, the right hand ball E25 thereof is forced off its seat and fluid is enabled to flow toward unit A through the restricted I23 of unit B, past the inboard seal d of that unit and through the associated dashpot vent ear to the chamber [3! of unit A permitting completion of the left hand stroke or unit A. Stalling of the unit B piston in any other than an extreme position also enables the unit A to continue operation. If the unit B piston stalls at the end of its rightward stroke (piston extension i ll thereof in the outboard dashpot sleeve) the piston of unit A will be supplied for return stroke through opening of the check valve 25 or unit B and thence through the bypass route as just described but without restriction at lS. If either piston position, it is evident from Fig. 8 that the bypass system operates ,as beforeto enable movement of the other piston in both directions. In such case, as the balls I24 and l 25 unclose, direct flow past the unseated ball through its bore I23 to the cross passage :29 is blocked by the sliding flt of the ball in said bore. of supply through a stalled piston to the other unit is controlled always least primarily by the size of the vent passages 22? and E28.

, Parking is controlled and effected exactly as with the previously described arrangement, being initiated by slowly closing the control valve 3, Fig. 1. Since at parking pressure both valves I24 and 125 are closed by their spring I32 fluid is trapped in the chamber I or the chamber l3i depending upon whether the parking position of pislon lid is at the right or left, the units being reversible in that respect. The check valve and spring arrangement enable the pistons H6 to be hydraulically locked in any position Within the capacity of the spring 132 to hold the balls I24 and I25 from being forced off their seats. The window units Iii] operate to main- ,tain or tend to maintain the wipers in synchronism irrespective of unequal loading in the same manner as do the previously described units, since, by opening the check valves, restricted amounts of fluid are free to by-pass either piston in opposite directions regardless of the relative positions of the pistons in their cylinders.

I claims 1. A pressure sensitive fluid circuit establishing. valving mechanism comprising two valves, biasing means initially maintaining the valves in a first circuit-establishing initial position, means whereby a rise in pressure of fluid in the established circuit moves the valves into a second circuit establishing position, valve-position-retaining means rendered operativeby said movement of one of the valves to hold the other valve in its moved position, and means operated by a rise in pressure in the second established circuit to release the position-retaining means and enable return of both valves by their biasing means to their initial position.

2. A pressure sensitive fluid 'circuit reversing Thus the rate (e. g. unit A) becomes stalled in a mid stroke valving mechanism comprising two spring biased valves initially maintained by their springs in a first circuit-establishing position, means whereby fluid pressure rise in the established circuit moves the valves into circuitreversing position, fluid trapping means rendered operative by said movement of one of the valves to hold the other valve in its moved position, and means operated by fluid presure rise in the reverse circuit to release the fluid trap-ping means and enable return of both valves to their initial position.

3. A fluid d recting valve mechanism for controlling distribution of operating fluid in a closed loop reciprocating servomotcr system wherein reciprocating motion results from alternately supplying exhausting fluid to and from opposite ends of the loop, said mechanism comprising a pair of spring biased valve plungers and cooperating ports and passages so arranged that a predetermined rise in pressure fluid in a flrst-established circuit in the loop first moves both plunger-s against the bias of their springs to a fluid-circuitreversing relative position in respect to the loop, port and pressure chamber means associated with one plunger and controlled by movement of the other plunger to its fluid reversing position to constitute a fluid trap operative to hold said one plunger in its said position, and other pressure operated means actuated by a rise in reversed circuit p assure in such loop for moving said other valve plunger to a second position in which the trapped fluid is released to enable the mechanism to re-cycle.

i. A pressure sensitiv fluid circuit reversing valving mechanism comprising two valve plungers normally held by respective springs in a first circuit-establishing position, pressure responsive means operatively associated with therespective plungers, communicating with the first circuit and open ted by a rise in pressure thereof to move both plungers into circuit-reversing relative position, fluid trapping valve means controlled by such movement of one of the plungers to hold the other plunger in its circuit-reversing position, and other pressure responsive means operatively connected with said one plunger, communicating with the second circuit and rendered operative by a predetermined rise in the pressure thereof to impart further movement to said one plunger, and valving means operated by said one plunger to release the trapped fluid whereby to enable return of saidother plunger to its first circuitestablishin position.

5. Reversing valve mechanism for fluid pressure operation of a reciprocating servomotor having its opposite ends connected in closed loop'circuit arrangement with the valve mechanism through a pair of service ports thereof acting alternately as supply and return ports, said mechanism comprising a spring biased directional valve normally positioned by its spring to divert supply pressure to-a first service port, a cooperating spring biased valve normally positioned by its spring to enable exhaustion through the valve mechanism of fluid through a second service port, pressure operated means respectively associated with the directional valve and cooperating valve and acting thereon, consequent upon a predetermined rise in pressure of fluid admitted to the mechanism, to move said valves to respective first operating positions reversing the supply and exhaust fluid c rcuits through the mechanism, position retaining means connected for operation by the cooperatin valve in its first operating position to hold the directional valve in its first operating position until the servomotor is blocked against further movement, and other pressure operated means acting on the cooperating valve consequent upon occ rence of such blocs g to move it to a pos won retaining-mes.ns-releasing second operating position enabling springreturn oi the directional valve to its normal position, thereby rendering inoperative both pressure operated means of the cooperating valve to enable return of the latter to its normal position.

6. A fiuid motor actuator unit comprising a body having a pressure iiuid inlet port, pressure fluid service ports and an exhaust fluid outlet port, with passages interconnecting said ports, a spring biased pressure operated d directing valve plunger, a spring biased slave valve plunger and a pressure operated serve-motor for positioning the slave plunger against the bias of its spring, said plungers being cooperatively movable to open and close valving ports of the body cornmunicating with said passages alternately to conmeet the service ports with the pressure inlet and exhaust port, the directing valve plunger being initially moved against its biasing spring by inlet pressure fluid to establish inlet pressure to one service port and the servomotor, the slave plunger thereby moving against its biasing spring to communicate the other servic port with a passage leading to the exhaust port, said slave valve plunger simultaneously trapping fluid in a manner to hold the directing valve in the stated position, said slave valve plunger having a piston portion communicating with pressure fluid being delivered to said one service port for operating the slave valve plunger in the same direction as the slave plunger is moved by the servomotor whereby to r lease the trapped fluid and enable spring return of said plungers and the servoinotor to their original positions.

'7. A fluid pressure 0' era-ted system comprising a plurality of servomotors arranged in series with each other and connected respectively with al ternately acting fluid supply and exhaust lines, reversing valve mechanism connected with said lines and operable automatically to supply and exhaustfiuid in respect thereto consequent upon a predetermined rise in fluid supply pressure alternately in said lines, each of said servoinotors comprising a cylinder and a piston reciprocatable 16 therein, and fluid operated servo-motor synchronizing means including axially extending primer passages in the pistons each having a, throttling valve port positioned to be closed by a cooperating cylinder surface as the pistons reach the ends of their s rokes in one direction, whereby to enable lay-passing movement of fluid in one of the pistons to and from opposite end spaces of its cylinder in event the throttling valve port of such one piston remains unclosed when the valve port of another piston is closed.

8. In combination with an automatic reversing valve for fluid in two service lines arranged to recycle itself upon a predeterminable rise in service line pressure, a plurality of piston and cylinder units in series and connected with said lines, the piston of each unit having a through bore, a pair of oppositely acting non-return valves in each bore opening from the outer end of each against a biasing means responsive to less pressure than the recycling pressure of the reversing valve and restricted vent passages associated with each nonreturn valve behind respective plugs thereof and arranged to enable lay-passing of operating iluid through one unit to another without stalling the other unit or recycling the reversing valve.

9. The combination according to claim 8 wherein each piston and cylinder unit has a restrictediiuid-venting dashpot at each end arranged to become respective parts of said vent passages when one piston is held in end stroke position While another piston is moving in its cylinder.

COLUMBUS R. SACCHINI.

REFERENCES CITED The following references are of record in the iile or" this patent:

UNITED STATES PATENTS Number Name Date 2,069,122 Weaver Jan. 26, 1937 2,169,451 Parker Aug. 15, 1939 2,202,023 Parker May 28, 1940 2,292,916 Wheelon Aug. ll, 1942 2,298,457 Borges Oct. 13, 1942 2,359,949 Van Der Werfi Oct. 10, 19% 2,446,611 Rose Aug. 10, 1943 2,516,558 Freedman July 25, 1950 2,516,594 Rose July 25, 1950 

